Milk quality from Yak and Zom milk in Bhutan

J Wangdi

Abstract

Milk composition has high importance in the making of dairy products.
Information related to Yak milk compositions is limited,with very few attempts
made to study it. The objective of this study was to report empirical information
on the composition and quality of Yak milk in Bumthang, one of the Yak rearing
districts of Bhutan, with the aim of using it as the basis for a
more detailed investigation of Yak milk and on the development of a niche
market for Yak dairy products in the country.

The average values in milk fromYak and Zom were 7.08 and 5.86 % fat, 10.6 and
10.4 % solids non-fat, 4.86 and 4.80% protein, 5.82 and 5.70% lactose, 0.81 and
0.84% other solids, freezing point of -0.724 and -0.697ºC and density of 1.34
and 1.033 kg/l, respectively. The average daily milk production was 1.09 kg for
Yak and 1.61 kg for Zom.

Keywords: crosbreed, milk analyzer, Yak, Zom

Introduction

Yak milk plays a very important role in the daily life of pastoralists,
locally known as Brokpas in -eastern and central-, Jobs
in
–western-, Dakpas, Merak and Sakteng in Tashigang
district and Lakhaps in west-central region of Bhutan. The milk is the
main source of protein for the household members of pastoralists. Fresh raw milk
is seldom consumed. Almost all milk produced is processed into dairy products:
butter, hard cheese - locally known as Chugo - and fermented cheese
called Yidpa. Milk surplus is either sold or bartered for basic
necessities within the village and nearby towns. Given the rugged
geo-topographical terrain, harsh climatic conditions and difficult accessibility
of the region, developing and promoting a high quality niche market for Yak
dairy products will enhanceYak herders’ income. Prior to developing a niche for
Yak dairy products it is necessary to establish the average composition and
quality of Yak´s milk. .Current information is limited, and very few attempts
have been made to determine the compositional quality of Yak´s milk in Bhutan.
Therefore, the objective of this study was to establish the baseline information
on the composition and quality of Yak´s milk. Comparisons were made with milk
from the Zom (crossbreed Yak Bos grunniens and Tibetan bull Bos
taurus).

Materials and methods

Milk samples were collected between April and September from 56 Yaks and 10
Zom (F1 of Yak x cattle), from three Yak herds in Chumey and Ura block of
Bumthang district. The females were of different age, lactation stage and parity
number, although under similar management practices all year round. The three
herds were located in the range of 2 hours walking distance from the human
settlement areas, selected to make data collection easier. The samples consisted
of 30 ml of milk collected from each animal. Milk samples were stored and
transported in a cool box to be analysed. The analysis was done after 2 hrs from
the collection, using automatic ultrasonic milk analyzer (Master Eco, India) at
an average sample temperature of 22 degree Celsius. The milk analyzer used in
this study has the capacity to measure the percentage of fat, solids non-fat,
protein, lactose and other solids, as well as the percentage of added water,
density and freezing point, in less than 2 minutes per sample. The
daily milk yield of Yak and Zom were also recorded using a spring balance with
10g precision.The data were analyzed using descriptive statistics in SPSS,
version 21 (George and Mallery 2014).

Figure 1. Yak (Bos grunniens).

Result and discussion

Average daily milk yield and milk composition

The Yak average daily milk yield was 1.09 kg (range from 0.3-2.3 kg) and 1.61 kg
(0.88-3.0 kg) for the Zom, the latter being higher than the 1.41 kg/day,
reported by Dorji (2000). The higher average daily milk yield of
Zom could be attributed to the heterosis resulting from crossbreeding between
Yak (Bos grunniens) and Tibetan bull (Bos taurus), figure 2; however, in
contrast milk components were found lower in Zom milk as compared to the Yak’s
milk. The herders in this study indicated that the Zom in general has longer
lactation length and produces higher daily milk of lower density as compared to
Yak. Correspondingly, the density of Zom milk (1.033 kg/l) recorded in this
study, was found lower than the Yaks’ milk (1.034 kg/l). Joshi
(1982) reported total milk yield of 720 kg in 180 days lactation for the Yak and
1300 to 1690 kg in 180 days lactation for the Chauri -cross of Yak (Bos
grunniens) and local hill cow (Bos indicus) and vice versa.

Figure 2. Zom is the the
cross of Tibetan bull (Bos taurus) with yak.

Figure 3. The male is
known as Zo, and it is reported to be infertile and used for draft
purpose.

Table 1. The daily milk yield and the
compositional quality of Yak and Zom’s milk

Parameters

Yak

Zom

n

56

10

Daily milk yield, kg

1.09 ± 0.05

1.61 ± 0.21

% Fat

7.08 ± 0.20

5.86 ± 0.55

% Solids non fat

10.62 ± 0.08

10.39 ± 0.19

Density, kg/l

1.034

1.033

Freezing Point ºC

-0.724 ± 0.01

-0.697 ± 0.02

% Protein

4.86 ± 0.03

4.80 ± 0.07

% Lactose

5.82 ± 0.04

5.70 ± 0.11

% Other solids

0.81 ± 0.01

0.84 ± 0.02

% Total solids

17.70

16.25

The fat content of Yak milk falls within the range of 5.5–7.5 % reported by
Li et al (2009), although the upper limit was found much higher in this study.

The protein content of Yak´s milk ranged from 4.40 to 5.1 %, about the same
as reported by Li et al (2009) and Nikkhah (2011). This author reported 16.9 -
17.7% for total solids, 4.9 - 5.3% for protein, 5.5 - 7.2% for fat, 4.5 - 5.0%
for lactose, and 0.8 - 0.9% for minerals.

Dong et al (2007) reported that the fat content varies around 6.5%, protein
and lactose about 5.5% and ash 0.8% in Yak milk. They also reported that the Yak
milk yield and their composition were affected by breed, age, parity and body
condition of cow, pasture growth and quality, milking time, milking methods and
environmental factors.

In this study the lactose content ranged from 5.2 to 6 %, higher than the 5%
reported by Nikkhah (2011), and quite the same as in the report of Dong et al
(2007).

The average total solids was 17.5 % for Yak milk, falling within the ranges
16.9–17.7 or 16.9 -17.7% reported by Li et al (2009) and Nikkhah (2011),
respectively. The finding of 0.81% ash was comparable to that of 0.8 % reported
by Dong et al (2007).

Conclusions

Yak milk had higher concentrations of solids non fat, fat, protein and
lactose content compared to Zoms’ milk. The total solids content of Yaks’ milk
was also high.

The rich nutrient content of Yaks’ milk will help to diversify its conversion
to different niche products of high value.

Acknowledgement

The author would like to acknowledge the herders for their support,
particularly for providing the milk samples free of cost; Mr. DB Gurung, E A
Chumey and Lhawang Dhendup (ex-Gup), Ura for arranging logistics for the
collection of milk samples; and the staff and management of the RNR-RDC, Jakar.

References

Dorji T 2000 Genotypic and phenotypic characterization of
the Yak (Bos grunniens) and Yak farming systems in Bhutan. MSc. Thesis. Institute
of Land and Food Resources, University of Melbourne, Australia.